Apex domains cannot have CNAME records.
Question and response
Question
dig 238.127.42.in-addr.arpa. NS
Answer
238.127.42.in-addr.arpa. 5 NS ns010-03sn149g9881d150.0.d-53.jp.
238.127.42.in-addr.arpa. 5 NS ns010-03sn149g9881d150.0.d-53.net.
238.127.42.in-addr.arpa. 5 NS ns010-03sn149g9881d150.0.d-53.info.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0